Vehicles with electrically variable transmissions are frequently driven by the transmission including the associated battery and motor/generators. Electric hybrid vehicles offer the potential for significant fuel economy improvements over their conventional counterparts. The hybrid systems use electric motors to drive the vehicle under certain conditions, and the vehicle engine is shut off to save fuel.
Under certain driving conditions the electric motors do not have the capacity to provide the power required by the vehicle. When the capacity of the electric motors is reached, the vehicle engine is started and the engine is used to drive the vehicle. However, a vehicle operating near the threshold of requiring power from the engine or able to be powered by the electrically variable transmission alone may cause the vehicle to frequently shift in and out of electrically variable mode.
Additionally, to enhance performance and fuel economy of the vehicle, the electrically variable transmission is operated in a first mode when the vehicle is in electric vehicle mode and in a second mode when the engine is operating. The first mode and the second mode may include differing commands for gear shift timing and other transmission operations. Continually switching the transmission between the first operating mode and the second operating mode not only reduces fuel economy but may also affect the smoothness of the vehicle ride.